Throughout history, the management of human waste has evolved to eliminate odor, reduce the chance for the spread of disease and pathogens, and provide less offensive waste removal.
The flush toilet virtually revolutionized civilization. Waterborne sanitation is often seen as the normal method for the disposal of human waste. Due to its “flush and forget” nature, it is often seen as the ideal solution for many applications. However, the strain on precious water resources and aquifers should not be underestimated. One person on average creates 550 liters of human waste every year. Over the course of a year, to flush away the 550 liters of human waste in a waterborne system requires approximately 15,000 liters of water. Added to this is the high cost of and need for, maintenance of the treatment plants and reticulation systems.
Not all situations can provide the running water and sewer or septic system required to support flush toilets. For example, campgrounds, cabins, recreational areas, remote areas, sports fields, fishing camps, marinas, construction sites, military venues and many other situations often require sanitation but do not have the infrastructure to support traditional flush toilets. In the nation's parks, recreation areas and campgrounds, waterborne sanitation is not always feasible due to water shortages or unavailability, pollution, costs, climatic conditions and impractical applications. The situation is even worse in less development countries.
The result has been the pursuit of alternative forms of sanitation such as pit latrines, composting toilets, chemical toilets and incendiary toilets. Each of these has its flaws. For example, many outdoor venues have pit latrines or porta-johns that need to be pumped periodically. Such arrangements are often odiferous and inconvenient and costly to maintain. It would be highly desirable to replace such systems with less costly designs that are easy to install and maintain and offer reduced odor.
Some in the past have developed evaporative toilets based on the concept that air can be used to evaporate moisture from the human waste, thereby reducing volume and pathogens. Unlike a conventional flush toilet which removes and relocates waste to a waste treatment installation such as a septic system or community treatment center, an evaporative toilet provides more self-contained non-discharge waste processing. Such designs are therefore more naturally suited for use in places where little or no waste removal and processing infrastructure is in place. Evaporative toilets work where there is no water, where the ground is rocky, on hills and mountains and with elevated or non-elevated structures and on shorelines. They are ideal for cabins, lodges, recreational and rest areas where there is no water for conventional sanitation. They were designed to mitigate sanitation-borne diseases and because the waste is dried rapidly (and possibly also due to aerobic bacteria effects), the pathogen levels are extremely low.
The waterless dehydration/evaporation toilet system thus provides a non-polluting, environmentally friendly, cost-effective and low maintenance solution to human sanitation. It offers a standard of respectability and convenience, comparable to a waterborne system, yet without the prohibitive costs and obvious strain on precious water resources.
One example of non-limiting evaporative toilet design provides dry sanitation in a sealed, zero-discharge unit that is driven by radiant heat and/or wind power. Such example non-limiting embodiments provide a solution to many areas confronted by sanitation problems. The human solid waste entering the unit is quickly separated from the urine, which is evaporated into the atmosphere. The solids, by a process of dehydration, dramatically reduce in volume. There are no odors and the material removed (for example, every two to three years or at other intervals, depending on number of users) is virtually pathogen free. Some non-limiting embodiments do not require chemicals, other additives or electricity. If over used, the liquids can be easily pumped and the evaporative process will begin again. Such systems are suited for remote areas such as campgrounds, where no electricity is available and only the sun and wind are available as energy sources.
As evaporative toilets have experienced increased use, it has become evident that further improvements in efficiency are both desirable and needed. In particular, an evaporative toilet unit installed in a low usage environment such as a single family cabin or vacation home may give long term trouble-free reliable service. That same unit installed in a popular campground, state park or other high usage area may experience significant problems. For example, an evaporative toilet unit installed in a high density area of a camp or campground may not be capable of processing high volumes of waste in short amounts of time, and thus may need pumping or other attention that it would be desirable to avoid.
Challenges for high efficiency evaporative toilets include: a need to remove moisture quickly and thoroughly from solids in order to eliminate the danger of disease and unpleasant odors; the need to evaporate liquids rapidly without putting anything into the ground; and the need to accommodate a large enough volume to make the system viable for general use in high usage environments.
Factors that influence the rate of evaporation include temperature, barometric pressure, relative humidity, and in some designs, wind velocity. For example, evaporating water requires 540 calories of energy per gram to let the water molecules move freely and evaporate. The amount of surface area exposed to moving air is an important factor in achieving higher evaporation rates. Barometric pressure affects the diffusion rate, which affects evaporation. Ambient air temperature could be much higher than that of the liquid within the unit tank, situated deeper in the ground. The higher the flow of unsaturated air over the surface of the water, the greater is the rate of evaporation. Thus, wind powered evaporative toilets generally will operate more efficiently in higher prevailing wind conditions. Additionally, higher humidity results in lower evaporation rate. Heating the air using solar heating or other heat sources can be used to artificially induce additional heat. These and other conditions affecting evaporative toilet efficiency thus include:                Positioning of the unit in relation to available direct sunlight        Number of daylight hours        Shaded hours by cloud cover        Shaded hours by trees or other buildings        Temperature achieved during the hours of sunlight        Wind velocity—ventilation        Relative humidity        Percentage concentration of liquids in the solids mass        Complications of evaluating air concentration        Partial pressure (of water) which is relative humidity.        
Many of these factors are outside of the control of the designer, since they depend on local weather, seasonality, installation location and other complicating factors. Accordingly, there is a need for more efficient evaporative toilet designs that work well under a variety of different conditions to more rapidly process waste and thereby accommodate heavy use conditions.
Exemplary illustrative non-limiting evaporative toilet technology herein provides several different non-limiting embodiments and implementations offering some or all of the following and other non-limiting features, solutions and advantages:                separation of liquids from solids        rapid heating of air, said heating internal to the unit        rapid evaporation of liquids and drying (dewatering) of solids with constant circulation to said heated air.        by elimination of moisture from solids, the bacterial growth that causes decay and odor is eliminated, reducing or eliminating the production of methane gas.        requires no water or chemicals, uses a minimal amount of electricity and puts nothing into the ground        use of internally heated air to achieve said rapid evaporation        expansion of the air to liquid surface area by use of a water absorbing media to enhance evaporation        internal heat source requiring minimal use of electricity        adaptability to use of solar panel as source of electricity        portability: unit simply plugs in to electrical plug and can be attached and detached from vent much like a clothes dryer        constant air flow, pulling air away from toilet and into the exhaust vent        a unique air flow pattern that draws hot air over solids and then over liquids for evaporation of moisture        an expansion of the liquid surface exposed to hot air, achieved through the use of wicks or other such media or other mechanisms        air exhaust system: a unique exhaust flow system that draws saturated air out of the system        a carousel approach in which solids drop into separate holding cups and rotate        microwave technology that allows solids to be treated in a single containing unit        a receptacle/heater technology that allows for catchment of solids in a drying receptacle bag for easy removal        a substantially enhanced capacity that allows for multiple uses before anything needs to be removed by way of dried shrunken solids or packaged wicks used for purposes of evaporating liquids        instant on-site treatment of sanitation that puts nothing into the ground and does not require plumbing        enhanced capacity: in one non-limiting example, a single unit has the capability to handle the needs of 10 people around the clock (60 or more uses)        only a toilet seat is utilized, eliminating the need for toilets and toilet bowls such as those made of porcelain, ceramics or plastic        air exhaust system: a unique exhaust flow system that draws saturated air out of the system by a fan utilizing a solar panel or conventional sources of electricity        an evaporative toilet comprising: three different technologies as options: a carousel model, a microwave model and a simplified model        a unique enclosure with drawers for accessing used wick packages and dried solids        an air flow design that draws air into the unit from the toilet seat area        a separate chamber for heating and drying solids, and a separate chamber for evaporating liquids        an air outlet coupled to said enclosure, said air outlet permitting air to circulate through said enclosure before being exhausted from said enclosure        a fan strategically placed to create a unique airflow that pulls air through the unit, first over solids and then over liquids        a unique wicking application than provides a greatly enhanced surface for exposure of liquids and solids to air        for carousel embodiments: a unique rotating tray, a unique design of the containers comprising the carousel and a unique circuitry design that allows stepped and uniform rotations in sync with heating lights inside the unit, and unique path for the liquids as they flow towards the drying chamber.        for microwave embodiments: a unique application of microwave technology in the drying and germ-killing of sanitary solids and liquids; a unique design of the containers comprising the solids chamber and liquids chamber; a unique circuitry design that allows the operation of levered catchment of human waste and timed bursts of microwaves; a unique anti-splatter device within the unit.        for direct heating embodiments: a unique method of heating and drying liquids through the use of a combined catchment receptacle/heater strategically placed in line with continuous air flow.        
The exemplary illustrative non-limiting technology herein addresses these and other challenges in a manner both different from and more efficiently than any other systems.